Movement within the musculoskeletal system is dependent upon functional joints. Significant pain can be associated with dysfunction joints and can present an individual with physical limitations. Pain caused by problems associated with the spine is a common ailment in adults and affects millions of individuals each year in the United States. The management of chronic back pain remains challenging even in view of currently available operative and non-operative techniques.
Various surgical procedures are used on patients having chronic back pain. These include (a) intradiscal procedures, which can include injections (epidurals), electrothermal exposure, and nerve stimulation; (b) fusion of the spine (arthrodesis); and (c) intervertebral disc excision (discectomy).
Medical procedures involving spine fusion have been practiced for many decades. However, these techniques remain controversial and the results remain unclear.
Intervertebral disc replacement is an attractive alternative to spine fusion. Disc replacement offers the advantages of restoration of segmental mobility in the spine, elimination of pain, and improvement in the distribution of biomechanical forces in the spine.
Approaches to restoration of the function of a degenerated or dysfunctional disc include biological reconstruction and artificial disc replacement. Prosthetic devices that can be used for the replacement of the intervertebral discs can be divided into two general categories. One category is devices that replace the nucleus only, leaving the annulus and cartilaginous portions of the endplate intact. A second category is devices that replace the entire intervertebral disc.
While artificial disc replacement is viewed as a distinct improvement over techniques such as spine fusion, many replacement processes are particularly invasive. Commonly performed replacement processes entail insertion of relatively large artificial discs. These invasive procedures can involve the significant resection of tissue in order to gain access to the injury site. This may increase the risk of complications, such as infection and spine trauma associated with the insertion of the disc. Furthermore, these procedures may require extensive hospitalization and therapy following the procedure. Given this, these more invasive procedures are only used in more serious cases of spine problems.
In addition to issues of invasiveness, many disc replacement techniques involve the use of biomaterials that are not ideally suited as replacement materials for a normal intervertebral disc. A normal intervertebral disc includes a nucleus, composed primarily of proteoglycans and Type II collagen with a capacity to absorb and distribute load, and an outer annulus with well-organized layer of Type I collagen that serve to stabilize the motion segment. The composition and arrangement of these natural tissues in a healthy intervertebral disc provide unique biomechanical properties. Currently available systems are not able to sufficiently mimic these properties of a normal intervertebral disc.